to be single, or at least without large families. And in developing countries there are generally pronounced age-cohort differences in educational attainment, so their education will be higher than that of the adult population as a whole. Finally, willingness to assume risk is linked to age, education, and employment, although it is formally distinct. Stated as a proposition: Forms of migrant selectivity, excepting sex, are interrelated, and when these variables change they will change in the same direction.
Data from the Monterrey study can be combined with Mexican census results to provide some useful comparisons for education and employment, as shown in Table 6. The categories are noncontiguous groupings of municipios (Mexican county equivalents) that are based on socioeconomic criteria. Category I represents highly urban and industrially advanced areas, whereas Category V includes highly rural and backward areas.
A detailed analysis of Table 6 is not possible here (see 17). What is important for our purposes is the demonstration that (a) migrants are selective on both education and employment, with selectivity being extreme for the earlier periods and for the less developed Categories III-V; and (b) excepting for comparisons in Categories I and II that can be explained, selectivity has declined substantially since 1941. In addition to these two variables, it was found that the more recent migrants to Monterrey were more likely to arrive at that place married; and if married, more likely to arrive with children; and if arriving with children, more likely to have two or more children upon arrival.
In all, the Monterrey data provide strong support for the argument that migrant selectivity has declined over the past several decades. The somewhat lengthy explanation of why this happened cannot be reproduced here, especially since it depends in part upon peculiarities of Mexican development. However, the shift from "pioneer" to "mass" migration does have some features of general application and significance. In the course of urbanization, the "reservoir" of rural potential migrants tends inevitably to decline relative to the ever-increasing demands placed upon it by sustained urbanization. Thus, as a larger proportion of the total population of the reservoir is drawn upon, the characteristics of the migrants come to resemble the average of that population. In the Monterrey case the number of migrants by time of arrival rose about sixfold in 30 years. The rural reservoir in the area states providing most of the migrants to Monterrey increased by little more than 50 percent during the same period.
This discussion leads to the following proposition: The lower the rate of out-migration from rural and small-town areas to large cities, the greater the selectivity. Stated another way: The longer a rapid rate of urbanization is maintained, the more probable a decline in selectivity of migrants from rural areas. Admittedly, the evidence for these propositions is limited, but they touch upon important, if often overlooked, features of migrant selectivity.tion rates would he lower.an, et al. (1 3, Ch. 1). Substantively, Ghana differs from Mexico in the predominantly male rural-urban migration, in the multilingual character of the society, in the existence of polygamy, and